CHICAGO (Reuters) - A high dose of the arthritis drug
Celebrex showed early signs that it may help prevent lung
cancer in heavy smokers, U.S. researchers said on Sunday.

The Pfizer Inc <PFE.N> drug, also known as celecoxib, works
by blocking the COX-2 enzyme that causes inflammation, which
has been linked with cancer.

A six-month study of 212 current or heavy smokers found a
reduction in a specific type of precancerous change in lung
cells in people who took a high dose of Celebrex compared with
those who took a placebo.

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None of the study participants had any heart-related
problems such as those with Merck & Co Inc's <MRK.N> now
withdrawn arthritis drug Vioxx, another COX-2 inhibitor.

"Celebrex was safe and we did not see any cardiovascular
events," said Dr. Edward Kim of M.D. Anderson Cancer Center in
Houston, who presented his findings at a meeting of the
American Society of Clinical Oncology in Chicago.

He said the study suggests that a high dose of Celebrex
might alter some of the cellular changes that lead up to lung
cancer. But the finding is very early and would need to be
confirmed in longer, larger studies.

"This is not a study where we go tell someone who is a
heavy smoker to start taking Celebrex to prevent lung cancer,"
Kim said in an interview.

Lung cancer is the leading cause of cancer death in the
United States, according to the American Cancer Society. In
2008, about 215,000 people will be diagnosed with lung cancer
and about 114,000 people will die from it.

The study was started before news emerged in September 2004
that Vioxx doubled the risk of heart attack and stroke in
certain patients.

Kim said the trial was put on hold in December 2004 at the
request of Pfizer and the National Cancer Institute, which
funded the trial, so the researchers could look for signs of
heart attacks or strokes.

It was started up again in May 2005 after the researchers
added safeguards, including consultations with cardiologists,
to reduce heart risks.

EARLY SIGNS

Rather than a direct measure of cancer prevention, which
could take many years, Kim said the researchers were looking
for early changes in the body that might suggest the drug could
reduce the chances of developing lung cancer.

Two large, long-running lung cancer prevention studies of
beta-carotene and vitamin A supplements found they actually
increased the risk of lung cancer.

"We have not had positive results with these studies. Now
we would like to search for an intermediate endpoint or
biomarker," Kim said at a media briefing.

"Perhaps that will lead us in the direction of who we need
to target in the future," he said.

The researchers tested Celebrex in the study because
studies in cells, mice and in people have shown the COX-2
enzyme is present at higher than normal levels in lung cancer
and in precancerous lesions of the lung, Kim said. COX-2 is
thought to play a role in the development of blood vessels that
feed tumors.

Kim's study measured levels of the Ki-67 protein, a marker
for cell growth. The researchers wanted to see if Celebrex had
an impact on levels of this protein in tissue samples taken
from the lungs of heavy smokers.

At the beginning of the study, the researchers took lung
samples from six predetermined areas of the lung.

People in the study either got a 200 milligram or a 400
milligram dose of Celebrex twice a day, or a placebo.

After three months, they took more lung samples, and they
took samples again at six months. Kim said the group that got
the higher dose of Celebrex saw a reduction in levels of the
Ki-67 protein.

Kim said it will be important to find better ways of
identifying people who are at the highest risk for lung cancer
for whom the benefits of taking a high-dose COX-2 inhibitor
would outweigh any potential heart risks.